Acoustical aid for deaf persons



I. P. IVIAXFIELD. ACOUSTICALAID FOR DEAF PERSONS.

APPLICATION FILED JAN. 2,I920y Patented July 18, 1922.

y [il: f KM `uurllso Vs'rATlis PATENT OFFICE.

JOSEPH iP. IMAXFIELD, OF'MAPLEWOOD, NEW JERSEY, ASSIGNOB T0 WESTERN ELEG` TRIO COMPANY, INCORPORATED, F NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

To all whom it may concern.'

Be it known that I, JOSEPH P. MAXFIELD, a citizen of the United States, residin at Maplewood, in the county of Essex and tate of New Jersey, have invented new and useful Improvements in Acoustical Aids for Deaf Personsfof which the following `is a full, clear, concise, and exact description.

This invention relates to devices for improving the hearing of deaf or 'partially deaf persons and its object is to bring such a person into 'natural acoustical relation to his environment.

Among the` many devices which have been developed as an aid to deaf persons the most successful has undoubtedly been -the type which which makes use of av small micro phonic telephone transmitter in combination with a head telephone receiver and a small dry battery. Such devices have however some serious defects, one of the most objectionable being that extraneous room noises and street noises are so blended in with the spoken sounds that it is extremly diiiicult for the listener to focus his attention on the speech and to separate it mentally from the extraneous disturbances. Another objection is that in order that these devices may produce a suiiicient volume of sound to give efective aid in hearing recourse has been had to extremely sensitive microphones-, which break badly when suddenly jarred or when they' are subjected to unusually loud sounds and thus produce disagreeable and often painfully loud shocks to the ear. IThese microphones are furthermore inherently liable to produce sizzling and frying f noises which'addn still further tothe dili-' greater magnitude so that sudden shocks and jars do not produce excessively loud sounds in the telephone receiver. This microphone is v,used in combination with a distortionless amplifier, preferably of the audion type,

'whose output is made adjustable to give any desiredV volume of sound depending on the sensitivenessof the ear the intensity of the sound and the .prevalence of disturbing noises. Preferably two of these microphone- Specification of Letters Patent.

ACOUSTICAL AID FOR DEAF PERSONS. v

Application eld January v2, 1920. Serial No. 348,868.

' amplifier systems are employed, each leading being connected to the right-hand microphone-amplifier and the `lefthandreceiver being connected to the left-hand microphone-A ampliier. The use of a binaural system of this sort has been found to` be remarkably efficient in enabling the user .to focus his attention on the particular soundx which `he desires to hear, for by orienting the dual microphone set so that. the microphones lie in a plane atright angles to the source of sound the same ability to concentrate is noticed as when a person of' normal hearing turns to face the speaker.

The binaural system has theA further advantage of enabling the` user to determine the direction from which a sound is coming,f to distinguish for example, which one of a number of persons is speaking. 'This effect is due not to a difference in theintensi'ty of the sound reaching the two ears but to the difference in phase of the sounds at the two ears, so that the advantages above noted are available to those who have morediiiiculty in hearing with one ear than with the other. Such differences in the sensitiveness of the two ears can, in the present invention, be

compensated for by adjusting the degree of..

amplification in the two amplifying circuits so that they will deliver a greater volume oit-sound to the less sensitive ear.

, The invention will be more clearly understood by referring to the accompanying drawing in which Fig. ll gives a diagram.-y

matic representation of the system of this invention; Fig. 2 shows in detail the construction ofone of the microphone elements,

asf

and Fig. 3 shows anarrangement for mounting the microphonesso that they may be oriented easily.

Referring-to Fig. 1, two microphones 4 and 5 are connected in series Awith batteries 6 and 7 and the rimary windings of induction coils 8 an 9 respectively. The secondary windings of the induction coils 8 and 9 are connected to the terminals of the reed cathodes 14, 1 5, control-:electrodes 16, 17, 1N

and anodes 18, 19. The temperature of the :filaments and consequently the output of the amplifiers can be readily adjusted bymeans of the rheostats 20, 21, located in the filament circuits. The output circuits of the amplifiers 12 and 13 are connected respectively to the primary windings ofthe transformers 22 and 23 while the secondary Windings ofthese transformers are connected to the two telephone receivers 24 and 25.

The microphones 4 and 5 are preferably of the air-damped type shown in Fig. 2 having a vibratory diaphragm 26 securely clamped between a perforated front plate 27 and a back plate 28. The spaces 29 and 30 between the diaphragm and the front and back plates respectively are made extremely small, of the order of .005 inch or less so that there is a thin layer of air on either side of the diaphragm which effectively limits the amplitude of its vibration. The back plate 28 is provided with an annular groove 31 which communicates with-the space 30 and acts as an air reservoir. This air reservoir series of small openings 32 located at intervals along its length.

The back plate 28 is furthermore provided with a central cavity 33 to accommodate the microphone button 34 which is adjustably mounted on the back plate 28 and insulated therefrom by the insulating washers 35 and 36. The microphone button 34 carries a fixed electrode 37 and a mass of granular carbon 38.v -The movable electrode 39 is attached to the diaphragm 26 or may be a gold plated surface thereon. Between the edge of the button cup'and the front electrode 39 is a resilient washer 40 preferably offelt.

The two microphones 4 and 5 are preferably mounted on a stand such as that shown in Fig 3 comprising a base portion 41 and an'upright standard 42 on which is mounted a rotatable collar 43 carrying laterally extending arms'44 to the ends of which the microphones 4 and 5 are attached. This -arran ement is primarily adapted to use on a tabl or desk and enables the user to orient the plane of the microphones so that it will lie at right angles to the 'direction from which thel sound, which it is desired to hear, is coming.

Vhat is claimed is:

l. A. system. for enabling a deaf person 1 ,aaasw to place 'himself in natural acoustical relation to his yenvironment comprising a pair of microphones mounted with their diaphragms in the same plane, means for changing the angular position of said plane with reference to a sound source, a pair of telephone receivers, one for each ear of said deaf person, and a separate circuit connecting each of said receivers with a corresponding one of said microphones.

2. A. system for enabling a de-af person to place himself in natural acoustical relation to his environment comprising a pair of microphones mounted with their-diaphragms in the same plane, means for changing the angular position of said plane with reference to a soundsource, a pair of telephone receivers, one for each ear of said deaf person, a separate circuit connecting each of said receivers with -a corresponding one of said microphones, and a current amplifier in each of said circuits.

3. A binaural system for .deaf persons comprising a pair of microphones having highly damped vibrating systems, a corresponding pair of telephone receivers, a separate amplifying circuit connecting each of said microphones withthe corresponding receiver, and means for adjusting the degree of amplifica-tion in said circuits.

4. A binaural system for deaf persons comprising a pair of microphones having air-damped vibrating systems, a corresponding pair of telephone receivers, a separate amplifying circuit connecting each of said microphones with the corresponding receiver, and means for'adjusting the degree of amplification in said circuits.

5. A system for enabling a deaf person to place himself in natural acoustical relation to his environment comprising a pair of\ microphones mounted with their diaphragms in the same plane, means for changing the angular position of said plane with reference to a sound source, a pair of telephone receivers, one for each ear of said deaf person, a separate circuit connecting each of said receivers with a corresponding one of said microphones, a current amplifier in each of said circuits, and means for adjusting the output of each of said amplifiers separately. ln witness whereof, I hereunto subscribe my name this 30th day of December A. D.

.rosari-i P. mixnmnn. 

